Medical radiation imaging scanners, for example (but not limitation), a computed tomography (CT) imaging scanner, a positron emission tomography (PET) imaging scanner, or a single photon emission computed tomography (SPECT) imaging scanner, can employ a high frequency electromagnetic energy source, for example (but not limitation), a neutron, electron, proton, X-ray, or gamma ray source, which emits a high-energy beam or particle toward a subject. PET and SPECT often employ a gamma-emitting tracer as a high-energy source. CT often employs a radiation source, such as an X-ray tube.
The high-energy beam, particle, or emission can impinge on one or more detectors. Often the beam, particle or emission impinges on a detector after being attenuated by a subject. Each detector can produce one or more electrical signals, based on the high-energy beam, particle, or emission received by the detector. The electrical signals can be processed to produce a useful image of the subject. The detectors, and in some cases the high frequency electromagnetic energy source, can be rotated around the subject to produce three-dimensional images of the subject.
The high-energy beam, particle, or emission received at the detector can be collimated with a collimator, so that only rays traveling parallel to a specified direction are allowed through. Collimators are used, because it is not yet possible to focus radiation with such short wavelengths into an image through the use of lenses as is routine with electromagnetic radiation at optical or near-optical wavelengths. The collimated beam can be directed to a scintillator. A scintillator is a material, which exhibits the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e. reemit the absorbed energy in the form of light. The light energy produced by the scintillator can be used to produce one or more electrical signals by an electronic light sensor such as a photomultiplier tube (PMT) or a photodiode. The electrical signals can be processed to produce a useful image of the subject.
State-of-the-art detector designs currently incorporate a reflective “seat” element that aids in the gathering of incoming photons as well as to mechanically position the photo sensor array. This “seat” can be constructed in numerous ways, including potting and injection molding. However, the primary characteristic driving the material choice for the “seat” is the reflectivity of the material. Materials with poor reflective characteristics negatively affect both the overall magnitude of the generated signal as well as the positioning of scintillation events—both critical to radiation detection. In general, mechanical properties such as thermal conductivity and strength are secondary considerations. As the detectors become more hybridized, new designs must make due with fewer structural elements; encompassing greater functionality, in order to fulfill spatial constraints. In addition, often the performance of new silicon based sensors is dependent upon the ability to control the surrounding temperature.
A need exists, therefore, for a medical imaging detector having a reflective optical mask layer independent of the “seat” structure. Such a geometry would allow for the optimization of the “seat” for both improved thermal conduction and/or improved mechanical properties, without sacrificing optical performance. It would be desirable to transfer the reflective optical mask away from the “seat.”